Glaucoma refers to a group of optic neuropathies that are characterized by loss of retinal ganglion cells and atrophy of the optic nerve with resultant visual field loss. The disease is the leading cause of irreversible blindness worldwide and the second leading cause of blindness, behind cataracts. Clinical trials have demonstrated that elevated intra ocular pressure (IOP) is a major risk factor for glaucoma, and have validated the role of lowering IOP in the management of glaucoma.
Glaucoma is classified according to three parameters: 1) the underlying cause, i.e., primary (idiopathic) or secondary (associated with some other ocular or systemic conditions); 2) the state of the anterior chamber angle, i.e., open angle (open access of the outflowing aqueous humor to trabecular meshwork) or closed angle (narrow angle; the trabecular meshwork is blocked by apposition of the peripheral iris and the cornea); and 3) chronicity, i.e., acute or chronic. Although secondary forms of glaucoma with clear etiologies do exist (e.g., pseudoexfoliation and pigmentary dispersion), the most common form of glaucoma is primary open angle glaucoma (POAG).
Ocular hypertension (OHT) is a condition in which IOP is elevated but no glaucomatous findings have been observed (Bell, 2005). The Ocular Hypertension Study demonstrated that patients with OHT have an overall risk of 10% over 5 years of developing glaucoma and that this risk can be cut in half by the institution of medical treatment that reduces IOP.
Accordingly, there remains a need for treatment effective against such disorders.